Inverter units are used in various applications such as in the control of a drive motor of, for example, a hybrid automobile, an electric vehicle, or the like. An inverter unit comprises a semiconductor (switch) device, such as an IGBT (insulated gate bipolar transistor), and a heat exchanger for cooling the semiconductor device as well as other heat generating elements (bodies) such as the electronic parts that constitute the power conversion circuit. The heat exchanger comprises a jacket, on the outer surface of which the heat generating elements are mounted, and a heat sink, which is housed inside the jacket. To improve the performance of the heat exchanger, production efficiency, and the like, the heat sink is usually joined to the jacket by brazing.
Such heat sinks are often configured as a plate-fin heat sink, in which multiple fin plates extend vertically (perpendicularly) from a base plate. In the past, this type of heat sink has been manufactured by extrusion. However, because there are restrictions on the shapes that can be manufactured with extrusion techniques, it is difficult to manufacture, for example, a heat sink in which the plate thickness of the fin plates is relatively thin, a heat sink in which the tongue ratio (i.e. the ratio of the height to the pitch of each fin plate) is large, or the like. Thus, in previously-known techniques, the restrictions on, for example, the shape, the pitch, the tilt, and the like of the fin plates disadvantageously decrease the number of degrees of freedom in the design of the heat sink.
Accordingly, to increase the number of degrees of freedom in the design of the heat sink, Japanese Laid-open Patent Publication 2013-116473 discloses a technique in which the fin plates and the base plate are separately prepared and are then integrated (joined) by brazing. In addition, Japanese Laid-open Patent Publication 2015-126050 and its counterpart US 2015/0189791 disclose a technique in which multiple fin plates are disposed such that they are spaced apart and parallel to one another and then are linked by rod-shaped linking members.